After the MIL-P-28809 issued with the ionic cleanliness test embedded in it,
users started to ask for component surface areas. In an effort to
simultaneously address this issue, as well as issue blanket approvals for the major ionic
cleanliness instruments. (The Navy was getting tired of issuing waivers to use
an automated test instrument for every contract that called out MIL-P-28809
instead of the original wash bottle technique). The result of a Navy study
issued as MRR 3-78 was the table of equivalence factors/ionic limits for the
different instruments still in use today.
The report also contained results for nine PWAs, characterized as follows:
Capacitor
Transistor (e.g. this one had 32 transistors on it)
Resistor
Power Transistor with Heat Sink
Cordwood Pack
Transistor with Pad
Edge Card Connector
DIP
Jumper Wire

Each of the test PWAs had a calculated are of the PWB plus the components.
The hope was that all component makers would get on board and issue a calculated
component area on their component spec sheets. Then it would be simple to
calculate and place the PWA area on the part drawing.
It proved more difficult than anticipated to get all the component makers to
participate in such a program.
Perhaps now with lead-free, each component that issues as a lead-free package
could have the component area calculated and placed on the new/revised spec
sheet for these components. Doing the work in an incremental fashion would not
present such a formidable task to the component makers/suppliers-- in fact, it
could be a competitive advantage to provide such information.

Bill Kenyon
Global Centre Consulting
3336 Birmingham Drive
Fort Collins, CO   80526
Tel: 970.207.9586   New Cell: 970.980.6373

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